The present invention relates to a polyolefin resin composition modified with a (co)polymer prepared from a copolymerizable monomer mixture comprising an xcex1,xcex2-monoethylenically unsaturated monomer and other copolymerizable monomer. More specifically, the invention relates to the resin composition used for a coating or primer of untreated polyolefin resin films, sheets and molded articles, or an adhesive.
Conventionally, polyolefin resins have good productivity, excellent moldability and many other advantages such as light weight, corrosion prevention and impact resistance, and are thus widely used for interiors and exteriors of automobiles and ships, home electrical appliances, furnitures, miscellaneous goods and building materials.
These polyolefin resin molded articles generally differ from polar synthetic resins represented by a polyurethane resin, polyamide resin, acrylic resin and polyester resin, and are nonpolar and crystalline. Consequently, general purpose coatings and adhesives are very difficult to coat or adhere these polyolefin resin molded articles.
As a result, in order to coat or adhere polyolefin resin molded articles, surface adhesion has been improved by primer treatment or activation of the surface. For example, automotive bumpers have enhanced surface adhesion to the coated film by etching treatment with a halogen based organic solvent such as trichloroethane, or desired coating or adhesion has been carried out after pretreatment such as corona discharge, plasma arc or ozone treatment.
However, these conventionally known coating and adhesion methods using a general purpose resin composition required high equipment cost and long application time, and additionally, lead to irregular finish and tend to cause local difference on the state of treated surface.
In order to solve the above problems, coating compositions have conventionally been proposed. For example, a composition obtained by introducing maleic acid into polyolefin has been disclosed in JP-B-62-21027/1987, and a composition having chlorinated polyolefin as a primary component has been disclosed in JP-B-50-10916/1975. However, these compositions are poor in weatherability, though excellent in adhesion properties to polyolefin molded articles. As a result, uses are usually limited to primer or to places where weatherability is not desired. When these compositions are used for coating places where weatherability is needed, a top coat is usually applied by using a two component system which requires complex operation.
Consequently, development of a coating has been carried out on a one component finishing system which can exhibit good adhesion properties to the material without any pretreatment and also has excellent weatherability. For example, a resin obtained by copolymerizing an acryl-based monomer with chlorinated polyolefin has been described in JP-A-58-71966/1983. A coating composition of a hydroxyacryl-chlorinated polyolefin copolymer and an isocyanate compound has been disclosed in JP-A-59-27968/1984.
Other proposals which have been made in the field are a process for introducing an unsaturated bond into polyolefin (JP-A-1-123812/1989 and 2-269109/1990), a process for introducing organic peroxide (JP-A-1-131220/1989) and a process for using bifunctional organic peroxide (JP-A-64-36614/1989). Any of these proposals are designs for improving reactivity of polyolefin with a radically polymerizable, unsaturated monomer.
However, in the above resin composition and the preparation process of the same, the reaction must be, in many cases, carried out in a dilute concentration particularly due to the problem of viscosity. As a result, graft polymerization efficiency to polyolefin is reduced and a homopolymer of the radically polymerizable, unsaturated monomer is liable to form. The resulting resin solution has a strong tendency to develop phase separation and usually has a disadvantage that the solution cannot be used as intact for coating.
The present invention provides a novel resin composition which can eliminate conventional problems mentioned above. That is, the resin composition of the invention can be applied to spray coating in a high concentration without developing a separation phenomenon of the resin solution, and can be used for coating, primer and adhesive. The film obtained by using the coating which comprises the resin composition of the invention and a curing agent capable of reacting with active hydrogen and/or a hydroxyl group can exhibit superior weatherability compared to a chlorinated polyolefin film and excellent adhesion properties compared to an untreated polyolefin resin film, sheet or molded article.
As a result of an intensive examination and investigation in order to achieve the above objects, the present inventors have found that the resin composition obtained by reacting a mixture of polyolefin and a specific (co)polymer, or a reaction mass resulting from polymerization of specific copolymerizable monomers in the presence of polyolefin under radical generation in the presence of in organic solvent, is very effective for achieving the above objects. Thus the invention has been completed.
That is, the present invention can be characterized by the following items (1) to (13).
(1) A resin composition characterized in being obtained by reacting polyolefin (A) with a (co)polymer (B) prepared from a copolymerizable monomer mixture (C) comprising an xcex1,xcex2-monoethylenically unsaturated monomer and other copolymerizable monomers, in a weight ratio (A)/(B) 1/9-9/1, under radical generation in an organic solvent.
(2) A resin composition characterized in being obtained by polymerizing a copolymerizable monomer mixture (C) comprising an xcex1,xcex2-monoethylenically unsaturated monomer and other copolymerizable monomers in the presence of polyolefin (A) in a weight ratio (A)/(C) 1/9-9/1 in an organic solvent, and successively by reacting the obtained reaction mass under radical generation.
(3) The resin composition according to item (1), wherein the (co)polymer (B) is modified to have a polymerizable unsaturated bond in the molecule.
(4) The resin composition according to item (3), wherein the modification is carried out by reacting a (co)polymer (B) having hydroxyl group in the molecule with a polymerizable unsaturated carboxylic anhydride.
(5) The resin composition according to anyone of items (1) to (4), wherein the resin composition comprises one or more third components selected from the group consisting of fats and fatty oils, derivatives of the same, epoxy resin and polyester resin.
(6) The resin composition according to item (5), wherein one or more third components have a polymerizable unsaturated bond in the molecule.
(7) The resin composition according to anyone of items (1) to (6), wherein the polymerization reaction under radical generation is carried out in the presence of organic peroxide.
(8) The resin composition according to item (7), wherein the organic peroxide has a tert-butyl and/or benzyl group.
(9) The resin composition characterized by removing the solvent from the resin composition in anyone of the items (1) to (8) and diluting the residue with an optional organic solvent.
(10) A coating characterized by comprising the resin composition according to anyone of items (1) to (9).
(11) A coated film characterized by applying the coating according to item (10).
(12) A coating characterized by consisting of a principal component comprising the resin composition having an active hydrogen atom and/or hydroxyl group according to anyone of items (1) to (9) and a curing agent capable of reacting with an active hydrogen atom and/or hydroxyl group.
(13) A coated film characterized by curing the coating according to item (12).
One of the resin compositions in the invention can be obtained by reacting polyolefin (A) with the (co)polymer (B) prepared from the copolymerizable monomer mixture (C) comprising an xcex1,xcex2-monoethylenically unsaturated monomer and other copolymerizable monomers in the presence of the organic solvent under radical generation.
Polyolefin (A) which can be used in the invention includes, for example, a homopolymer or copolymer of ethylene, propylene, 1-butene, 1-heptene, 1-octene, 1-hexene, 1-decene and 4-methyl-1-pentene. These homopolymer and copolymer can comprise diene such as butadiene. Particularly, on preparing coating, primer and adhesive which are used for coating polypropylene materials, polyolefin (A) which can be preferable used is polypropylene or a copolymer having 50% by weight or more of propylene component.
The above polyolefin preferably has a weight average molecular weight (hereinafter referred to simply as Mw) in the rage of 5,000 to 200,000. When Mw is less than 5,000, the resin, composition obtained is liable to have poor adhesion properties to the material to be coated. On the other hand, Mw exceeding 200,000 gives high viscosity even in relatively low concentration on dissolving polyolefin into a solvent in the step of resin synthesis. Thus, preparation of the desired resin composition becomes difficult.
The (co)polymer (B) which can be used for the invention is prepared from an xcex1,xcex2-monoethylenically unsaturated monomer or a copolymerizable monomer mixture (C) comprising an xcex1,xcex2-monoethylenically unsaturated monomer and other copolymerizable monomers.
Representative xcex1,xcex2-monoethylenically unsaturated monomers which can be used for preparing the (co)polymer (B) in the invention include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and other (meth)acrylic acid esters; hydroxyethyl acrylate, 2-hydroxyethyl (meth)acrylate and other hydroxyvinyl compounds; acrylic acid, methacrylic acid, maleic acid, itaconic acid and other carboxyvinyl compounds and monoesters of the same; styrene, xcex1-methylstyrene, vinyltoluene, tert-butylstyrene and other aromatic vinyl compounds; and other compounds such as acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, acrylamide, mathacrylamide, methylolacrylamide, methylolmethacrylamide, ethylene, propylene and C4 to C20 xcex1-olefin.
Exemplary other copolymerizable monomers which constitute (co)polymer (B) in the invention include maleic anhydride, phthalic anhydride, succinic anhydride, and other carboxylic anhydrides which can copolymerize with xcex1,xcex2-monoethylenically unsaturated monomer.
The xcex1,xcex2-monoethylenically unsaturated monomer and other copolymerizable monomer which can be used in the invention exhibit radical polymerization property. The description methyl (meth)acrylate indicates methyl acrylate and methyl methacrylate.
The (co) polymer (B) in the invention can be prepared by using these monomers singly or as a mixture. For example, known acrylate resin can be used as a (co)polymer (B) of the invention.
The (co)polymer (B) prepared from these monomers can be modified to introduce a polymerizable unsaturated bond in the molecule. The modified (co)polymer (B) can also be used as a (co)polymer (B) of the invention. The (co)polymer prepared from hydroxymethyl acrylate, hydroxyethyl (meth)acrylate or other hydroxyvinyl compounds has a hydroxyl group in the structural units of the polymer molecule. The modified (co)polymer (B) can be prepared by addition of maleic anhydride, phthalic anhydride, succinic anhydride or other polymerizable unsaturated dicarboxylic anhydride to the hydroxyl group of the (co)polymer, by reacting the hydroxyl group with a remained isocyanate group resulting from reaction of a urethane resin having two isocyanate groups with a resin or monomer having a polymerizable unsaturated bond and hydroxyl group, or by other known processes.
The above hydroxyl group containing (co)polymer (B) has a hydroxyl value in the range of preferably 1 to 200 KOH mg/g, more preferably 5 to 150 KOH mg/g as solid.
The resin composition of the invention can be prepared by mixing the above polyolefin (A) and the (co)polymer (B) in an organic solvent in weight ratio (A)/(B)=1/9 to 9/1, preferably (A)/(B)=2/8 to 8/2, heating the mixture to 80 to 200xc2x0 C., and reacting under radical generation. When the ratio (A)/(B) is less than 1/9, the adhesive or coating obtained from the resin composition has poor adhesion properties to the substrate. On the other hand, the ratio (A)/(B) exceeding 9/1 is also unfavorable because weatherability becomes poor and adhesion to the top coat falls down.
The solvent which can be used in the invention includes, for example, xylene, toluene, ethylbenzene and other aromatic hydrocarbon; hexane, heptane, octane, decane and other aliphatic hydrocarbon; cyclohexane, cyclohexene, methylcyclohexane and other alicyclic hydrocarbon; ethanol, isopropyl alcohol, and other aliphatic alcohol; and methyl ethyl ketone, methyl isobutyl ketone and other ketone solvents. A mixture of these solvents can also be used. In these solvents, aromatic hydrocarbon and aliphatic hydrocarbon can be preferably used. A particularly preferred solvent is aliphatic hydrocarbon having 6 to 20 carbon atoms. The organic solvent can be used in such an amount that the solution of polyolefin (A) in an organic solvent has an non-volatile content in the range of 2 to 70% by weight.
On carrying out a radical reaction, radical generation method which can be used is, for example, photo-irradiation in the presence of a photo-polymerization initiator, addition of organic peroxide, or other known methods.
Representative photo-polymerization initiators include, for example, benzoyl, benzoin methyl ether, benzoin isopropyl ether, benzyl, benzophenone, 2-hydroxy-2-methylpropiophenone, 2,2-diethoxyacetophenone, benzyl methylketal, anthraquinone, chloroanthraquinone, ethylanthraquinone, butylanthraquinone, diphenyl sulfide, dithiocarbamate, 2-chlorothioxanthon, xcex1-chlromethylnaphthalenanthracene, 3,3xe2x80x2,4,4xe2x80x2-tetrabenzophenone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide. These initiators can be used singly or as a mixture. Michler""s ketone, trimethyleneamine, alkylmorpholine, and other amine compounds can also be used in combination with these initiators.
The amount of the above photo-polymerization initiator is in the range of usually 0.01 to 10% by weight, preferably 0.1 to 5% by weight for the total weight of polyolefin (A) and (co)polymer (B). When the amount of photo-polymerization initiator is less than 0.01% by weight, the resulting resin solution is liable to develop a separation phenomenon. On the other hand, the amount exceeding 10% by weight tends to cause gelation.
Exemplarily organic peroxide includes compounds having a tert-butyl and/or benzyl group in the molecule, for example, di-tert-butyl peroxide, tert-butylperoxy-2-ethylhexanoate, benzoyl peroxide, dicumyl peroxide, tert-butylperoxybenzoate and cumene hydroperoxide. These peroxides can be used singly or as a mixture.
In the above organic peroxide compounds, di-tert-butyl peroxide and tert-butylperoxy-2-ethylhexanoate are more preferably used in the invention. That is, the organic peroxide having a tert-butyl and/or a benzyl groups in the molecule has a relatively high hydrogen drawing ability and is effective for improving grafting ratio to polyolefin. By using these peroxide compounds, the resin composition obtained becomes very difficult to develop separation phenomenon.
The amount of the above organic peroxide is in the range of usually 2 to 50% by weight, preferably 3 to 30% by weight for the total amount of polyolefin (A) and (co)polymer (B). When the amount of the organic peroxide is less than 3% by weight, the resulting resin solution is liable to exhibit separation phenomenon. Further, addition of the organic peroxide at one time is liable to cause gelation of the reaction mixture. Thus, addition is preferably carried out many times by small portions over a long time.
Another resin composition of the invention can be obtained by polymerizing a copolymerizable monomer mixture (C) comprising an xcex1,xcex2-monoethylenically unsaturated monomer and other copolymerizable monomers in the presence of polyolefin (A) in an organic solvent and successively reacting under radical generation in an organic solvent.
The xcex1,xcex2-monoethylenically unsaturated monomer and other copolymerizable monomers which are used for preparing the above-mentioned (copolymer (B) can also be used in the copolymerizable monomer mixture (C).
The organic solvent used for polymerizing the copolymerizable monomer mixture (C) in the presence of polyolefin (A) can be the same as the organic solvent used for the reaction of polyolefin (A) and the (co)polymer (B).
Polymerization initiators are used for starting polymerization of the copolymerizable monomer mixture (C) in the presence of polyolefin (A). Representative polymerization initiators include, for example, di-tert-butyl peroxide, tert-butylperoxy-2-ethylhexanoate, benzoyl peroxide, dicumyl peroxide, lauroyl peroxide, tert-butylperoxybenzoate, cumene hydroperoxide and other organic peroxide compounds; azobisisobutyronitrile, 4,4xe2x80x2-azobis(4-cyanopentanoic acid), 2,2xe2x80x2-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] and other azo compounds. These initiators can be used singly or as a mixture.
In one of the preparation process of the resin composition in the invention, the above organic solvent solution of polyolefin (A), the copolymerizable monomer mixture (C) and the above polymerization initiator are simultaneously fed to the reaction zone and polymerization of the monomer mixture (C) is carried out under a constant weight ratio; polyolefin (A)/copolymerizable monomer (C) which is in the range of 1/9 to 9/1, more preferably 2/8 to 8/2.
When the ratio (A)/(C) is less than 1/9, the resultant coating or adhesive has poor adhesion to substrate. On the other hand, the ratio exceeding 9/1 is also unfavorable because weatherability becomes poor and adhesion properties to the topcoat are impaired.
The resin composition of the invention can be prepared by reacting thus obtained resin mixture under radical generation in an organic solvent similarly to the above reaction of polyolefin (A) and copolymer (B). The resin composition obtained by such process has much improved stability and low viscosity as compared with the resin composition obtained by reaction of (co)polymer (B) and polyolefin (A). Consequently, coating operation can be carried out in a high concentration.
One or more materials selected from the group consisting of oils and fats, derivatives of the same, epoxy resin and polyester resin can be added as a third component in the stage of polymerizing the copolymerizable monomer mixture (C) in the presence of polyolefin (A) and/or the stage of reaction under radical generation.
Representative oils and fats which can be used as the third component include, for example, linseed oil, soybean oil and castor oil and purified products of these oils.
Exemplarily derivatives of oils and fats which can be used for the third component include short-, medium- and long-oil alkyd resins which have a skeleton consisting of polybasic acid such as phthalic acid and polyhydric alcohol such as ethylene glycol, glycerol and pentaerythritol and are modified with fatty acid in oils and fats; further modified alkyd resins obtained by further modifying these modified alkyd resins with natural resin, synthetic resin or polymerizable monomer, for example, rosin-, phenol-, epoxy-, acryl- and urethane-modified alkyd resins.
When adding carboxylic anhydride having polymerizable unsaturated bond in the molecule to oils and fats having hydroxyl groups, the resulting oils and fats having polymerizable unsaturated bond can also be used for the invention. The above oils and fats and derivatives of the same, can be used singly or as a mixture.
Representative epoxy resins which can be used for the third component include epoxy resins obtained by reacting bisphenol A, bisphenol F or novolak with glycidyl ether, or obtained by adding propylene oxide or ethylene oxide to bisphenol A and successively reacting with glycidyl ether. Other epoxy resins which can be used include amine modified epoxy resin obtained by addition of polyfunctional amine to an epoxy group, aliphatic epoxy resin, alicyclic epoxy resin and polyether-based epoxy resin.
Still another epoxy resin which is obtained by addition of polymerizable unsaturated carboxylic anhydride to the above hydroxylated epoxy resin and has polymerizable unsaturation in the molecule can also be used in the invention. The above epoxy resins can be used singly or as a mixture.
The polyester resin which can be used for the third component can be obtained by polycondensation of a carboxylic acid ingredient and alcoholic ingredient. The carboxylic ingredient includes, for example, terephthalic acid, isophthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, 1,10-decanedicarboxylic acid, cyclohexanedicarboxylic acid, trimellitic acid, maleic acid, fumaric acid and other polycarboxylic acids and lower alcohol ester of the same; p-oxybenzoic acid and other hydroxycarboxylic acids; and benzoic acid and other monocarboxylic acids. These acids can be used singly or as a mixture.
The alcohol ingredient includes, for example, ethylene glycol, diethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 3-methylpentanediol, 2,2xe2x80x2-diethyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, neopentylglycol, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, propylene oxide adduct of hydrogenated bisphenol A and ethylene oxide adduct of hydrogenated bisphenol A. These alcoholic ingredients can be used singly or as a mixture.
The invention can also use a polyester resin which is obtained by addition of carboxylic anhydride having polymerizable unsaturated bond in the molecule to the above hydroxyl group containing polyester resin and has a polymerizable unsaturated bond in the molecule.
The above polyester resin can be used singly or as a mixture.
The third component above can be added by feeding to a reactor or can be previously charged to the reactor. The amount of the third component is usually 0.5 to 60% by weight, preferably 5 to 40% by weight for the resin component.
The third component can also be added after radical generation step.
When oils and fats or derivatives of the same are used for the third component, the resulting resin composition has particularly excellent stability, good compatibility with other resins, and extremely enhanced peel strength. Specifically, castor oil containing resin composition is very excellent.
The resin composition of the invention can be used as intact for coating, primer or adhesive. The resin composition prepared from hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylic acid or methacrylic acid and having an active hydrogen atom and/or a hydroxyl group in the resin can be used for coating in combination with a curing agent capable of reacting with an active hydrogen atom and/or a hydroxyl group. For example, polyurethane-based coating, primer or adhesive can be used by mixing the resin composition with a polyisocyanate-based curing agent capable of reacting with an active hydrogen atom and/or a hydroxyl group.
Representative polyisocyanate-based curing agents which can be used include, for example, phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate and other aromatic diisocyanates; hexamethylene diisocyanate, trimethylhexamethylene disocyanate, lysine diisocyanate and other aliphatic diisocyanates; and isophorone diisocyanate, dicyclohexylmethane diisocyanate and other alicyclic diisocyanates. Isocyanate terminated prepolymer obtained by reacting the above diisocyanate compounds with polyhydric alcohol, polyetherpolyol or polyesterpolyol can also be used.
Amino resin prepared from melamine or urea can also be used as a curing agent.
The resin composition of the invention and the curing agent capable of reacting with an active hydrogen atom and/or a hydroxyl group can be used in an arbitrary ratio.
When the curing agent capable of reacting with an active hydrogen atom and/or a hydroxyl group has an isocyanate group, the equivalent ratio of an active hydrogen atom to an isocyanate group is preferably in the range of 0.5:1.0 to 1.0:0.5, more preferably 0.8:1.0 to 1.0:0.8.
When the curing agent capable of reacting with active hydrogen atom and/or a hydroxyl group is an amino resin, the weight ratio of resin composition of the invention/amino resin as solid is preferably in the range of 95/5 to 20/80, more preferably 90/10 to 60/40.
The above obtained resin composition of the invention can be used as intact for coating, primer and adhesive. However, the resin composition can be incorporated, when needed, with additives such as an antioxidant, weatherability improver, heat stabilizer and other various species of stabilizers; inorganic pigment, organic pigment and other colorants; and carbon black, ferrite and other electrically conductive fillers.
No particular restriction is imposed upon the method for coating the surface of molded articles with the resin composition of the invention or with a mixture of the resin composition of the invention and the curing agent capable of reacting with an active hydrogen atom and/or a hydroxyl group. Spraying method is favorable. For example, coating can be carried out by spraying with a spray gun on the surface of molded articles. Application can be usually carried out with ease at room temperature. No particular limitation is put upon the drying method after application. Natural drying, forced drying by heating and other suitable methods can be used.
The resin composition of the invention and the mixture of the resin composition and the curing agent capable of reacting with an active hydrogen atom and/or a hydroxyl group can be used due to the characteristics thereof for a broad field of primer in addition to the above uses for coating. For example, the dried surface obtained above can be further painted with other coatings by electrostatic deposition, spraying or brushing. Other coatings which can be used are not restricted in particular and include, for example, solvent type thermoplastic acrylate resin coating, solvent type thermosetting acrylate resin coating, acryl-modified alkyd resin coating, epoxy resin coating, polyurethane resin coating and melamine resin coating.
Further, the resin composition of the invention or the mixture thereof and curing agent capable of reacting with an active hydrogen atom and/or a hydroxyl group can be favorably used for a topcoat of molded articles prepared by using, for example, polyethylene, polypropylene, polystyrene and other polyolefins; ethylene-propylene copolymer, ethylene-butene copolymer, propylene-butene copolymer, ethylene-propylene-butene copolymer and other olefin copolymers; and mixture of polypropylene and synthetic rubber, and can also be used for surface treatment of polyamide resin, unsaturated polyester resin, polycarbonate resin and a steel plate or a steel plate treated by electro-deposition.
Further more, the resin composition of the invention or the mixture thereof and curing agent capable of reacting with active hydrogen atom and/or a hydroxyl group can be used for a primer of coating and adhesive which consist primarily of polyurethane resin, polyester resin, melamine resin or epoxy resin. Such primer can improve adhesion properties of coating to various species of coated surface of articles and at the same time can form a coated film having excellent brilliancy.
The resin composition of the invention or the mixture thereof and curing agent capable of reacting with active hydrogen atom and/or a hydroxyl group can be favorably used in particular for a topcoat of molded articles prepared by using polypropylene and other polyolefin, a mixture of polypropylene and synthetic rubber, unsaturated polyester, epoxy resin and polyurethane resin, and also for a primer for improving adhesion properties of the topcoat to the surface of these molded articles.